This application is based on Japanese Patent Application No. 2003-92126 filed on Mar. 28, 2003 and Japanese Patent Application No. 2003-388000 filed on Nov. 18, 2003, the disclosure of which are incorporated herein by reference.
The present invention relates to a variable valve timing controller that changes opening and timing of intake valves and/or exhaust valves of an internal combustion engine according to operating condition of the engine. The opening and closing timing is referred to as valve timing, the variable valve timing controller is referred to as the VVT controller, and the internal combustion engine is referred to as an engine hereinafter.
The VVT controller is disposed in a torque transfer system which transfers the torque of the driving shaft of the engine to the driven shaft which opens and closes at least one of an intake valve or an exhaust valve. The VVT controller adjusts the valve timing of the valves by varying a rotational phase of the driven shaft to the driving shaft.
One of the conventional VVT controller varies the rotational phase by oil pressure. In such a VVT controller, it may be difficult to precisely control the oil pressure when it is under the sever condition such as low temperature and just after engine starting.
JP-U-4-105906 shows a VVT controller which varies the rotational phase of the driven shaft against the driving shaft by an electric motor. A stator of the electric motor makes a magnetic field which applies a torque to a motor shaft, and the torque is transmitted to a planetary gear mechanism to vary the rotational phase.
In this type of the VVT controller, when the magnetic field is not formed due to the electrical shorting or break of the stator coil, it is impossible to control the rotational phase by the planetary gear mechanism. Thus the rotational phase of the driven shaft may shift to the phase wherein it as impossible to start the engine.
The present invention is made in view of the above matters, and it is an object of the present invention to provide the VVT controller which can start the engine even in case of trouble.
If the stator fails to form magnetic field, a resistant torque arises on the motor shaft. Receiving the resistant torque, a phase converter shifts the rotational phase of the driven shaft toward the safety phase in which the engine can be started. Thus, even if the magnetic field is not formed due to the electrical shorting or break of the stator coil, the phase shift from the phase wherein the engine can be started into the phase wherein the engine can not be started is prevented.